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#1
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Glow Plug Lights Always On
Bad Relay? Is it repairable? Car just started running after more than 3 years. It wasnt like that before. Left it in a shop, got it back with lights always on now. They said they had a hard time starting it.
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'85 300D Cal 280,000 miles '14 GLK 350 60000 miles |
#2
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The glow plug light is always lit when the car is running.
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'85 300D Cal 280,000 miles '14 GLK 350 60000 miles Last edited by my123ca; 01-16-2010 at 08:30 PM. |
#3
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I'd begin with a standard diagnosis of the glow system similar to what is described on dieselgiant's site. I'd check for voltage the plugs with the key in glow and no glow position and check the ohm's on each plug. Report back.
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1977 300d 70k--sold 08 1985 300TD 185k+ 1984 307d 126k--sold 8/03 1985 409d 65k--sold 06 1984 300SD 315k--daughter's car 1979 300SD 122k--sold 2/11 1999 Fuso FG Expedition Camper 1993 GMC Sierra 6.5 TD 4x4 1982 Bluebird Wanderlodge CAT 3208--Sold 2/13 |
#4
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Pre-glow relay
The glow plug light is controlled by a temperature-sensitive timer in the relay; it normally stays on for 5-10 seconds. The relay keeps the glow plugs on for about 30 seconds, that is, the glow plugs stay energized even after the light goes out. If it's quiet in the car, you can hear the relay click off and if you have the dome light on, it will noticeably brighten.
A glow plug light that stays on all the time suggests a faulty glow plug (or several) or pre-glow relay, confirmed by the shop's comment that the engine was hard starting. I would first check the 80 Amp strip fuse in the pre-glow relay and also the fuses in the under-hood fuse panel. The card in my '85 doesn't list a fuse for the electronic part of the pre-glow relay but I think there is one (can anyone confirm?). The pre-glow relay does not always detect a single failed glow plug; you might have had a bad one for awhile and just didn't know about it -- the OM617 engine starts fairly well on 4 good glow plugs. If a second glow plug fails, the pre-glow relay will detect that and the engine also will become harder to start. Jeremy
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"Buster" in the '95 Our all-Diesel family 1996 E300D (W210) . .338,000 miles Wife's car 2005 E320 CDI . . 113,000 miles My car Santa Rosa population 176,762 (2022) Total. . . . . . . . . . . . 627,762 "Oh lord won't you buy me a Mercedes Benz." -- Janis Joplin, October 1, 1970 |
#5
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Just finished testing resistance(?) of the glow plugs. They all have a range of 0.9 -1.1 ohms. Check for continuity also. They were good. Checked for voltage to the pins. They all have the same voltage. The strip fuse is also good. Just wondering if a weak battery can cause the GP lights to stay on. I had to jump start the car to bring it home. It wont start right now.
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'85 300D Cal 280,000 miles '14 GLK 350 60000 miles |
#6
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Quote:
Since your battery is drained, I'm going to say your GP relay is bad and is always on which is causing the light to always be on. This would cause a drain on the battery.
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2009 ML320 Bluetec 1985 300CD 1981 300TD Past Mercedes 1979 300TD 1982 300TD 2000 E320 4Matic Wagon 1998 E430 1984 300SD 1980 300SD |
#7
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x2. However, in the cases of the relay staying on that I recall being posted on this forum, the glowlight did not stay on. Perhaps this is a different kind of failure in the relay. It should be simple to test. Start the car and after 4 minutes or so, check for voltage at the glowplugs.
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1977 300d 70k--sold 08 1985 300TD 185k+ 1984 307d 126k--sold 8/03 1985 409d 65k--sold 06 1984 300SD 315k--daughter's car 1979 300SD 122k--sold 2/11 1999 Fuso FG Expedition Camper 1993 GMC Sierra 6.5 TD 4x4 1982 Bluebird Wanderlodge CAT 3208--Sold 2/13 |
#8
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Quote:
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2009 ML320 Bluetec 1985 300CD 1981 300TD Past Mercedes 1979 300TD 1982 300TD 2000 E320 4Matic Wagon 1998 E430 1984 300SD 1980 300SD |
#9
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Check the DIY ....
That wizard of all posters, jbach36, wrote a great piece, explaining all about the glow plug process and changing them out. See the DIY post section in this forum.
jbach36 rocks! |
#10
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New battery-Started car. Car started immediately. GP light is still on. Checked for voltage at the 5 pins. They all have voltage after 5 minutes. Time for a new relay? I read somewhere in the forum that the relay is repairable, something about changing a capacitor? Opened up the relay and nothing looks burned inside.
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'85 300D Cal 280,000 miles '14 GLK 350 60000 miles |
#11
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ground connection
check your ground gonnection
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1986 300SDL, 211K,Dealership serviced its whole life 1991 190E 2.6(120k) 1983 300D(300k) 1977 300D(211k) |
#12
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Have a reference for that?
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#13
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could be the ground. I had the transmission rebuilt. Probably forgot to put the grounding strap. ACC blower doesnt work and the charging light is on also. Will check later.
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'85 300D Cal 280,000 miles '14 GLK 350 60000 miles |
#14
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The charging light being on suggests the voltage regulator assembly with the brushes is bad. Especially if it is barely one and goes off now and then, kind of as the engine speed picks up. Brushes wear out and then only intermittently make contact - adds resistance to the circuit and you don't have the juice needed to run the car off the alternator. Thus, the dash "charging" light comes on.
This is likely a separate problem from the one that has your glow plugs energized all the time. I would think the fuse would melt under those conditions though. Jim
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Own: 1986 Euro 190E 2.3-16 (291,000 miles), 1998 E300D TurboDiesel, 231,000 miles -purchased with 45,000, 1988 300E 5-speed 252,000 miles, 1983 240D 4-speed, purchased w/136,000, now with 222,000 miles. 2009 ML320CDI Bluetec, 89,000 miles Owned: 1971 220D (250,000 miles plus, sold to father-in-law), 1975 240D (245,000 miles - died of body rot), 1991 350SD (176,560 miles, weakest Benz I have owned), 1999 C230 Sport (45,400 miles), 1982 240D (321,000 miles, put to sleep) |
#15
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I second the "check the ground strap"
Furthermore if you do check the strap and it is ok, look into the alternator issue. It could very well be the brushes on the regulator. I just replaced a regulator in my 300SD. AL117X, regulator: 1197311028. It went from having to "bump" the pedal to get anything out of the alternator to getting 14v when the car was started without touching the pedal. As far as the relay goes, I suggest, if you have access to, going through the FSM's diagnostic for the relay. Also, it might be wise to remove the relay and clean the contacts on top. I had to do this on one of mine to get it to work. I thought it had failed but I ended up sanding the fuse contacts and terminal 30 screw, using q-tips to get the crud out of the 4/5 pin connector areas and finally using battery terminal cleaner to freshen up the pins. Reinstalled, fired right up, no problem.
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Cruise Control not working? Send me PM or email (jamesdean59@gmail.com). I might be able to help out. Check here for compatibility, diagnostics, and availability! (4/11/2020: Hi Everyone! I am still taking orders and replying to emails/PMs/etc, I appreciate your patience in these crazy times. Stay safe and healthy!) 82 300SD 145k 89 420SEL 210k 89 560SEL 118k 90 300SE 262k RIP 5/25/2010 90 560SEL 154k 91 300D 2.5 Turbo. 241k 93 190E 3.0 235k 93 300E 195k |
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